I'm wondering how far I can go into the Brotherhood questline before a point of no return. I'm playing on a multi-faceted sniper/assault character who will, eventually, be using powered armor. However her main loyalty is to the Railroad and Minutemen.

I know the quest has you destroy the railroad (I've beaten the main story as a Brotherhood loyalist) but I hadn't done anything on them previously. I'm wondering if there's a chance to go to them and "Spare" them, or is simply initiating that quest enough to burn that bridge?

You can do up to the Paladin Danse plot.

Then they'll ask you to take out the Railroad.

You can't accept that mission.

I was going to go to them and warn them but it said I was now Enemies with the Railroad, so I had to reload.

This is useful intel, thank you.